HOMOLOGY. 81 



grasping, every bone of one animal, no matter 

 how modified, or for what purpose employed, 

 may generally be compared with a correspond- 

 ing bone in any other. Yet these digits, as in 

 some hoofed animals, are sometimes found in so 

 rudimentary a form that it is difficult to suppose 

 that they can be of any use to the animal.* 



Again, in nearly all Vertebrata, whether the 

 neck is as long as in the giraffe, or as short as in 

 the whale, it is composed of seven vertebrse. 

 Yet, this rule admits of exceptions, thus showing 

 that it is not invariable, and that the real 

 explanation of this uniformity is not to be 

 sought for in the direction of the theory of an 

 archetype. The number of the sacral vertebrse 

 is more variable ; in man there are five, but in 

 the ostrich, Apteryx, and their allies, from 

 seventeen to twenty. 



A stronger instance of the persistence of 

 homological resemblances which appear to 

 answer no good end, is the presence in some 

 animals of rudimentary organs, which are not 

 only quite useless, but absolutely injurious to 



* This class of argument must be taken for what it is worth, with 

 the qualification that we are continually discovering the use of arrange- 

 ments in nature which formerly appeared to be purposeless. 



Gr 



